Roll Observatory packages and add a roll script

packages/observe/CHANGELOG.md

+#### 0.13.1+2
+
+ * Update to analyzer '<0.27.0'
+
+#### 0.13.1+1
+
+ * Update to logging `<0.12.0`.
+
+#### 0.13.1
+
+ * Update to analyzer `<0.26.0`.
+
+#### 0.13.0+2
+  * Fixed `close` in `PathObserver` so it doesn't leak observers.
+  * Ported the benchmarks from
+    [observe-js](https://github.com/Polymer/observe-js/tree/master/benchmark).
+
+#### 0.13.0+1
+  * Widen the constraint on analyzer.
+
+#### 0.13.0
+  * Don't output log files by default in release mode, and provide option to
+    turn them off entirely.
+  * Changed the api for the ObserveTransformer to use named arguments.
+
+#### 0.12.2+1
+  * Cleanup some method signatures.
+
+#### 0.12.2
+  * Updated to match release 0.5.1
+    [observe-js#d530515](https://github.com/Polymer/observe-js/commit/d530515).
+
+#### 0.12.1+1
+  * Expand stack_trace version constraint.
+
+#### 0.12.1
+  * Upgraded error messages to have a unique and stable identifier.
+
+#### 0.12.0
+  * Old transform.dart file removed. If you weren't use it it, this change is
+    backwards compatible with version 0.11.0.
+
+#### 0.11.0+5
+  * Widen the constraint on analyzer.
+
+#### 0.11.0+4
+  * Raise the lower bound on the source_maps constraint to exclude incompatible
+    versions.
+
+#### 0.11.0+3
+  * Widen the constraint on source_maps.
+
+#### 0.11.0+2
+  * Widen the constraint on barback.
+
+#### 0.11.0+1
+  * Switch from `source_maps`' `Span` class to `source_span`'s `SourceSpan`
+    class.
+
+#### 0.11.0
+  * Updated to match [observe-js#e212e74][e212e74] (release 0.3.4), which also
+    matches [observe-js#fa70c37][fa70c37] (release 0.4.2).
+  * ListPathObserver has been deprecated  (it was deleted a while ago in
+    observe-js). We plan to delete it in a future release. You may copy the code
+    if you still need it.
+  * PropertyPath now uses an expression syntax including indexers. For example,
+    you can write `a.b["m"]` instead of `a.b.m`.
+  * **breaking change**: PropertyPath no longer allows numbers as fields, you
+    need to use indexers instead. For example, you now need to write `a[3].d`
+    instead of `a.3.d`.
+  * **breaking change**: PathObserver.value= no longer discards changes (this is
+    in combination with a change in template_binding and polymer to improve
+    interop with JS custom elements).
+
+#### 0.10.0+3
+  * minor changes to documentation, deprecated `discardListChages` in favor of
+    `discardListChanges` (the former had a typo).
+
+#### 0.10.0
+  * package:observe no longer declares @MirrorsUsed. The package uses mirrors
+    for development time, but assumes frameworks (like polymer) and apps that
+    use it directly will either generate code that replaces the use of mirrors,
+    or add the @MirrorsUsed declaration themselves. For convinience, you can
+    import 'package:observe/mirrors_used.dart', and that will add a @MirrorsUsed
+    annotation that preserves properties and classes labeled with @reflectable
+    and properties labeled with @observable.
+  * Updated to match [observe-js#0152d54][0152d54]
+
+[fa70c37]: https://github.com/Polymer/observe-js/blob/fa70c37099026225876f7c7a26bdee7c48129f1c/src/observe.js
+[0152d54]: https://github.com/Polymer/observe-js/blob/0152d542350239563d0f2cad39d22d3254bd6c2a/src/observe.js
+[e212e74]: https://github.com/Polymer/observe-js/blob/e212e7473962067c099a3d1859595c2f8baa36d7/src/observe.js